The spout, as understood in this industry, is the entire rotatable part of a two swivel-spout dispensing closure. For clarity of description applicant has chosen to define this spout as comprising a knuckle and a nozzle extending outwardly therefrom.
Dispensing closures of the type to which the invention relates generally comprise a pivotal cylindrical knuckle with a nozzle extending therefrom and a base with which it is associated for swiveling movement. These are of a resilient, but generally shape-retaining material, e.g. polyethylene or polypropylene, which enables the knuckle at the inner end of the nozzle to be snapped into a substantially matching cavity in the base, the cavity wall having an arc greater than 180.degree.. In a preferred form the base is polypropylene and the spout is polyethylene. In any case, these parts must be so constructed and arranged that leakage is to be avoided.
Closures of the type herein discussed are molded in production quantities, and the two parts are assembled by automatic machinery. The bearing openings in which the knuckle rotates necessitate re-entrant portions in the base mold so that, when the core is "pulled" following casting, it is inevitable that slight departures from established tolerances may be expected. When this occurs, the manufacturer has what are termed in this industry as "leakers," by reason of the knuckle not sealing properly with respect to the base. That is to say, what was intended to be a reliable fit of the knuckle in its bearing openings then turns out to be less than perfect, with consequent rejection at the manufacturing or customer level. Heretofore, the attainment of this paramount objective left much to be desired. Even the provision of a protuberant, restricted area, such as a ring or pad, between the two parts to achieve high contact pressure per unit area has not resulted in adequate sealing. If the pads retaining the knuckle should apply too much force normal to the surfaces in contact in the neighborhood of the fluid passages through the base and spout, the resulting friction renders manipulation difficult and, if too little force, leakage occurs. This problem is minimal in the case of viscous fluids but is of considerable significance in the case of volatile fluids such as naphtha.
Prior to the present invention, U.S. Pat. Nos. 3,111,245 and 3,502,248 disclosed spouts which attempted to resolve the conflict between ease of movement and maintenance of the necessary seal U.S. Pat. No. 3,502,248 relies on several pads to support a solid cylindrical knuckle. Although the knuckle of U.S. Pat. No. 3,502,248 is supported on a plurality of pads, these latter are all tangent to the knuckle and, therefore, in the interest of conciseness, may be considered jointly as a cylindrical surface and the surface of the knuckle as a surface complementary therewith.